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Express.js Open Redirect in malformed URLs

Moderate severity GitHub Reviewed Published Mar 25, 2024 in expressjs/express • Updated Mar 27, 2024

Package

npm express (npm)

Affected versions

< 4.19.2
>= 5.0.0-alpha.1, < 5.0.0-beta.3

Patched versions

4.19.2
5.0.0-beta.3

Description

Impact

Versions of Express.js prior to 4.19.2 and pre-release alpha and beta versions before 5.0.0-beta.3 are affected by an open redirect vulnerability using malformed URLs.

When a user of Express performs a redirect using a user-provided URL Express performs an encode using encodeurl on the contents before passing it to the location header. This can cause malformed URLs to be evaluated in unexpected ways by common redirect allow list implementations in Express applications, leading to an Open Redirect via bypass of a properly implemented allow list.

The main method impacted is res.location() but this is also called from within res.redirect().

Patches

expressjs/express@0867302
expressjs/express@0b74695

An initial fix went out with [email protected], we then patched a feature regression in 4.19.1 and added improved handling for the bypass in 4.19.2.

Workarounds

The fix for this involves pre-parsing the url string with either require('node:url').parse or new URL. These are steps you can take on your own before passing the user input string to res.location or res.redirect.

References

expressjs/express#5539
koajs/koa#1800
https://expressjs.com/en/4x/api.html#res.location

References

@wesleytodd wesleytodd published to expressjs/express Mar 25, 2024
Published to the GitHub Advisory Database Mar 25, 2024
Reviewed Mar 25, 2024
Published by the National Vulnerability Database Mar 25, 2024
Last updated Mar 27, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS score

0.044%
(11th percentile)

CVE ID

CVE-2024-29041

GHSA ID

GHSA-rv95-896h-c2vc

Source code

Credits

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